Effects of desiccation and rehydration on nitrogen fixation by epiphylls in a tropical rainforest.

Nitrogen fixation rates by epiphyllous microorganisms are affected by desiccation. Rates from leaf samples which had been dried for 12 h were 0.66 ng N/10 cm(2)/h. In contrast, rates from leaves which had been kept continuously wet were 18.69 ng N/10 cm(2)/h. Leaf samples which had been rehydrated for 2 and 4 h showed intermediate fixation rates (4.26 and 9.76 ng N/10 cm(2)/h, respectively). Epiphyllous bryophytes maintain moist conditions on the leaf surface and thus create a microenvironment suitable for prolonged fixation by the microorganisms.